"Energetic" compounds are used extensively in a wide variety of applications, e.g., in explosive formulations, propellants, gas-generating compositions, and the like. It is generally preferred that such materials have a high energy content yet be relatively insensitive to impact, such that accidents are avoided and energy is released only when intended. The requirements of insensitivity and high energy are in conflict, making the development of new energetic materials a difficult and challenging synthetic problem.
In developing new energetic compounds, a number of factors come into play. For example, heats of formation, density, melting and decomposition temperatures, carbon content and, generally, nitrogen content, are properties which must be considered. Energetic compounds should display good thermal and shock properties, have high heats of formation, and be straightforward to synthesize in bulk. It is generally preferred that an energetic compound have a melting point above about 100.degree. C., an exothermic heat of combustion and a positive heat of formation .DELTA.H.sub.f, and a high decomposition temperature, with a relatively large separation between melting point and decomposition temperature preferred such that an energetic composition may be melt cast from the selected compound. Finally, it is of course preferred that an energetic compound be relatively simple and straightforward to synthesize in high yield.
A number of energetic compounds are known as useful as oxidizers, explosives and the like. Energetic compounds have also been disclosed as useful to inflate automobile and aircraft occupant restraint bags. However, previously known materials are generally limited in one or more ways, e.g., they are overly impact-sensitive, difficult to synthesize on a large scale, not sufficiently energetic, or the like. In addition, energetic compositions used to inflate occupant restraint bags in automobiles and aircraft typically contain potentially toxic heavy metal igniter materials, e.g., mercury compounds, Pb(N.sub.3).sub.2 or the like.
The present invention provides a new class of compounds which overcomes the aforementioned limitations in the art. The energetic compounds to which the invention pertains are commonly referred to as "secondary" explosives, i.e., compounds whose energy is released after activation by initiator compounds, also termed "primary" explosives. The compounds now provided herein meet all of the above-mentioned criteria, and outperform conventional energetic compounds in a number of ways. For example, higher O.sub.2 density is provided than obtained with conventional secondary explosives such as ammonium perchlorate. In addition, the novel compounds are highly energetic while not overly impact-sensitive, and are straightforward to synthesize in high yield.
In addition, the compounds of the invention undergo denitration in the body, releasing nitric oxide (NO); the compounds may accordingly be used as pharmaceutical agents, i.e., as so-called "NO-donors." NO donors are useful as vasodilating agents, insofar as NO activates guanylyl cyclase, increasing intracellular levels of cyclic guanosine 3', 5'-monophosphate (cGMP), and cGMP brings about smooth muscle relaxation. Previously known NO donors include, for example, nitroglycerin (glyceryl trinitrate), isosorbide dinitrate, isosorbide-5-mononitrate, erythrityl tetranitrate, pentaerythritol tetranitrate, sodium nitroprusside, S-nitroso-N-acetylpenicillamine (SNAP), linsidomine chlorohydrate (also known as SIN-1), and the so-called "NONOates," complexes of nitric oxide and nucleophiles that contain the N.sub.2 O.sub.2 -group and release NO upon heating or hydrolysis without need for activation. The pharmacological application of many known NO donors is limited, however, as a result of unwanted side effects, an undesirable NO release profile, or the like. Thus, there is a continuing need in the art for improved pharmaceutical agents useful as vasodilators.